Nontoxic Obscurant Compositions and Method of Using Same

ABSTRACT

A composition of matter capable of producing a nontoxic smoke upon combustion comprising a smoke formulation. The composition of matter further comprises an oxidizer selected from the group consisting of potassium chlorate and sodium chlorate. The smoke formulation further comprises a fuel.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

The U.S. Government has a paid-up license in this invention and theright in limited circumstances to require the patent owner to licenseothers on reasonable terms as provided by the terms of “Replacement ofRed Phosphorus in Smoke Producing Munitions” US Marine Corps Phase ISBIR Contract # M67854-07-C-6521.

TECHNICAL FIELD

The present invention relates to compositions that produce an obscurantcloud upon combustion and a method of making obscurant devices based onsaid composition.

BACKGROUND ART

Obscurants are compounds that are capable of blocking, scattering,and/or absorbing light and are often leveraged in military operations.Obscurants can aid with friendly operations by, for example, providingcover for troop movement, concealing the location and size of friendlyforces, concealing valuable facilities from enemy forces, and markingtargets. Obscurants can also obstruct and disrupt enemy operations by,for example, interfering with enemy communications and coordination.

Naturally occurring obscurants, such as fog, snow, or rain areunpredictable, and in many geographic locations, infrequent. As such,artificial obscurants are common in military operations. Artificialobscurants may be selected to block electromagnetic radiation in thevisible spectrum (approximately 0.38 μm to approximately 0.78 μm), thenear infrared spectrum (NIR) (approximately 0.78 μm to approximately 3μm), the mid infrared spectrum (MIR) (approximately 3 μm toapproximately 50 μm), the far infrared spectrum (FIR) (approximately 50μm to approximately 1000 μm), or a combination thereof.

Modified versions of traditional weapon delivery systems are used todeploy obscurants in the field. The explosive payload of variousmunitions, including grenades, rockets, and other artillery, are removedand replaced with a payload comprising an obscurant composition. The useof a particular munition type depends on the particular use. Forexample, obscurant grenades may be employed in small scale tacticalcombat operations. Rockets, mortars, or large scale artillery carryingobscurant composition payloads may be used to conceal or protect largeareas, such as air fields or large scale troop movements. Upon ignitionor detonation, the obscurant composition burns to produce a cloud ofsmoke that blocks a given spectrum of light.

Obscurant compositions currently used by the military include whitephosphorous (WP), red phosphorous (RP), hexachloroethane (HC), andterephthalic acid (TA). These obscurants exhibit a number of undesirableproperties, including high toxicity, poor shelf life, and high burntemperatures.

When white phosphorous burns in air, it produces a hydroscopic compound,diphosphorus pentoxide. As the diphosphorus pentoxide absorbs moisturefrom the atmosphere, small airborne droplets of phosphoric acid areformed. White phosphorous, however, is pyrophoric at relatively lowtemperatures. It will ignite in air at about 30° C., making it hazardousto handle, store, and transport.

Red phosphorous (RP) has largely replaced white phosphorous forobscurant purposes. Over time red phosphorous slowly degrades to highlytoxic phosphine gas, a pyrophoric gas that can self ignite when mixedwith air.

All phosphorous-based obscurants (both red and white) have a number ofother drawbacks. First, because they burn at high temperatures (>500°C.) and have a high flame front, they pose the risk of burning nearbypersonnel or noncombatants, damaging nearby buildings or equipment, andigniting secondary fires. Second, the resulting obscurant cloud iscomposed of acidic water vapor, which is a respiratory irritant.Inhalation of this vapor can pose a health threat to nearby personneland civilians.

Hexachloroethane-based obscurant compositions (HC) are produced bycombining hexachloroethane, aluminum powder, and zinc oxide. Uponcombustion, the mixture produces zinc chloride, which in turn absorbsmoisture from the air to form an obscurant cloud. The zinc chloride inthe resulting cloud is lethal if inhaled, capable of causing grosspathological pulmonary injuries and death due to pulmonary edema.Hexachloroethane-based obscurants, like the phosphorous-basedvariations, also have a high combustion temperature.

Terephthalic acid-based obscurants (TA), unlike phosphorous-based andhexachloroethane-based obscurants, produce a nontoxic smoke. However,terephthalic acid-based obscurants have limited obscuring properties ascompared to WP, RP, or HC.

The rate or production of obscuring smoke produced by conventionalobscurants is largely dependent on the packing density of thecomponents. Obscurant devices with higher packing densities produceobscurant smoke at a higher rate. Packing densities, however, aredifficult to control in practice and generally result in inconsistentresults. Moreover, obscurant devices with varying rates of smokeproduction (i.e., a initial high production rate followed by a slowersustaining rate) are likewise difficult to produce with any reliabilityby varying packing densities.

Accordingly, it would be an advance in the state of the art to providean obscurant composition for use in traditional applications that (i)burns at a lower temperature than existing compositions, (ii) produces anon-toxic obscurant cloud, (iii) equals or outperforms existingcompositions in obscuring performance, (iv) remains stable during longterm storage, (v) is capable of producing variable smoke productionrates without relying on packing density, (vi) is produced from nontoxiccomponents, (vii) is environmentally friendly, and (viii) is costcompetitive with existing obscurants.

SUMMARY OF THE INVENTION

An embodiment of the present invention provides a composition of mattercapable of producing a nontoxic smoke upon combustion. The compositionof matter comprises a smoke formulation. In certain embodiments,Applicant's smoke formulation comprises melamine and methyl gallate. Thecomposition of matter further comprises an oxidizer selected from thegroup consisting of potassium chlorate and sodium chlorate. The smokeformulation further comprises a fuel. The fuel comprises sucrose.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be more fully understood by referring to thefollowing Detailed Description of Specific Embodiments in conjunctionwith the Drawings, of which:

FIG. 1 is a graph comparing % transmittance over time for one embodimentof Applicant's obscurant formulation against conventional obscurants;

FIG. 2 is a graph comparing the minimum % transmittance for oneembodiment of Applicant's obscurant formulation against conventionalobscurants;

FIG. 3 is a graph comparing recovery time to 10% transmittance for oneembodiment of Applicant's obscurant formulation against conventionalobscurants;

FIG. 4 is a graph comparing minimum % transmittance for one embodimentof Applicant's obscurant formulation against various obscurantformulations, including those based on the individual components ofApplicant's smoke formulation;

FIG. 5 is a graph of mass extinction coefficient across the visible andnear infrared spectrum for various embodiments of Applicant's obscurantformulation compared to terephthalic acid, a conventional obscurantcomposition;

FIG. 6 is a graph of mass extinction coefficient across the visible andnear infrared spectrum for multiple tests of red phosphorous, aconventional obscurant composition;

FIG. 7 is a graph showing thermal aging results of Applicant's obscurantformulation;

FIGS. 8( a) and 8(b) are ternary plots showing various burn rates ofApplicant's obscurant formulation achieved by varying the relativeamounts of oxidizer, fuel, and coolant components;

FIG. 9 shows the molecular structure of example melamine derivativesused in various embodiments of Applicant's obscurant formulation;

FIG. 10 shows a polymerization reaction between melamine and a melaminederivative that occurs in one embodiment of Applicant's obscurantformulation;

FIG. 11 shows amine-containing melamine derivatives for use in variousembodiments of Applicant's smoke formulation;

FIG. 12 is a flowchart showing an exemplary method for producing adual-burn rate obscurant device capable of producing an initial heavysmoke screen followed by a lower sustaining smoke screen;

FIG. 13 is a graph comparing the minimum % transmittance for variousembodiments of Applicant's obscurant formulation, including embodimentscontaining 1% and 5% of various dicarboxylic acids;

FIG. 14 is a graph comparing recovery time to 10% transmittance forvarious embodiments of Applicant's obscurant formulation, includingembodiments containing 1% and 5% of various dicarboxylic acids;

FIG. 15 is a graph comparing the minimum % transmittance for variousembodiments of Applicant's obscurant formulation, including embodimentscontaining dimethylsulfone;

FIG. 16 is a graph comparing recovery time to 10% transmittance forvarious embodiments of Applicant's obscurant formulation, includingembodiments containing dimethylsulfone;

FIG. 17 is a graph comparing the minimum % transmittance for variousembodiments of Applicant's obscurant formulation, including embodimentscontaining Bisphenol S;

FIG. 18 is a graph comparing recovery time to 10% transmittance forvarious embodiments of Applicant's obscurant formulation, includingembodiments containing Bisphenol S;

FIG. 19 is a graph comparing the minimum % transmittance for variousembodiments of Applicant's obscurant formulation, including embodimentscontaining diphenylsulfone;

FIG. 20 is a graph comparing recovery time to 10% transmittance forvarious embodiments of Applicant's obscurant formulation, includingembodiments containing diphenylsulfone;

FIG. 21 is a graph comparing the minimum % transmittance for variousembodiments of Applicant's obscurant formulation, including embodimentscontaining Bisphenol A;

FIG. 22 is a graph comparing recovery time to 10% transmittance forvarious embodiments of Applicant's obscurant formulation, includingembodiments containing Bisphenol A;

FIG. 23 is a graph comparing the minimum % transmittance for variousembodiments of Applicant's obscurant formulation, including embodimentscontaining 5-Methoxy MeGallate or THEIC; and

FIG. 24 is a graph comparing recovery time to 10% transmittance forvarious embodiments of Applicant's obscurant formulation, includingembodiments containing 5-Methoxy MeGallate or THEIC.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

This invention is described in preferred embodiments in the followingdescription with reference to the Figures, in which like numbersrepresent the same or similar elements. Reference throughout thisspecification to “one embodiment,” “an embodiment,” or similar languagemeans that a particular feature, structure, or characteristic describedin connection with the embodiment is included in at least one embodimentof the present invention. Thus, appearances of the phrases “in oneembodiment,” “in an embodiment,” and similar language throughout thisspecification may, but do not necessarily, all refer to the sameembodiment.

The described features, structures, or characteristics of the inventionmay be combined in any suitable manner in one or more embodiments. Inthe following description, numerous specific details are recited toprovide a thorough understanding of embodiments of the invention. Oneskilled in the relevant art will recognize, however, that the inventionmay be practiced without one or more of the specific details, or withother methods, components, materials, and so forth. In other instances,well-known structures, materials, or operations are not shown ordescribed in detail to avoid obscuring aspects of the invention.

Applicant has developed an obscurant formulation based on nontoxiccomponents that is capable of producing a nontoxic cloud with excellentobscuring properties. In one embodiment, Applicant's formulationcomprises a powdered melamine/methyl gallate obscurant additive combinedwith a sucrose/chlorate fuel-oxidizer system. Upon ignition, the heatproduced by the combustion of the fuel causes the melamine/methylgallate to sublime, producing an obscurant smoke. The melamine/methylgallate mixture sublimes at a relatively low temperature, therefore theburn temperature of Applicant's formulation is lower than conventionalobscurants and produces a minimal flame front.

The following Example is presented to further illustrate to personsskilled in the art how to make and use the invention. This Example isnot intended as a limitation, however, upon the scope of Applicant'sinvention.

Example 1

In one embodiment, a 70/30 weight percentage ratio melamine/methylgallate formulation is prepared using the components in Table 1.

TABLE 1 70%/30% Melamine/Methyl Gallate Formulation Component TypeComponent Wt. % Quantity (g) Combustion Sucrose 39.20 3.92 ComponentSodium Chlorate 35.40 3.54 Smoke Melamine 15.70 1.57 Formulation MethylGallate 6.70 0.67 Binder Ethyl Cellulose 3.00 0.30 IntermediateIsopropanol — 10.8 Solvent Toluene — 3.54

Preparing the Smoke Formulation

The sucrose, sodium chlorate, melamine, and methyl gallate arepre-ground to a fine powder and passed through a #70 (212 μm) meshsieve. The powdered sucrose, sodium chlorate, melamine (1), and methylgallate (2) are added to a mortar and pestle and gently mixed forapproximately 5-10 minutes. In one embodiment, potassium chlorate isused as the oxidizer in the combustion component. In one embodiment, amixture of potassium chlorate and sodium chlorate is used as theoxidizer in the combustion component.

The sucrose is confectionary sugar sold in commerce by Sysco FoodServices. Sodium chlorate is sold in commerce by Gallade Chemical.Melamine is sold in commerce by US Chemical. Methyl gallate is sold incommerce by Dudley Chemical.

The formulation in Table 1 contains a weight percentage ratio ofcombustion component to smoke formulation of 77/23. In variousembodiments, the weight percentage ratio of combustion component tosmoke formulation ranges from at or between 80/20 to 60/40. A shift inthe ratio toward increased combustion component will result in a fasterburn rate, increased burn temperature, and an increased flame front. Inone embodiment, the weight percentage ratio of combustion component tosmoke formulation is about 80/20. In one embodiment, the weightpercentage ratio of combustion component to smoke formulation is about75/25. In one embodiment, the weight percentage ratio of combustioncomponent to smoke formulation is about 70/30. In one embodiment, theweight percentage ratio of combustion component to smoke formulation isabout 65/35. In one embodiment, the weight percentage ratio ofcombustion component to smoke formulation is about 60/40.

The formulation in Table 1 contains a weight percentage ratio ofmelamine to methyl gallate or 70/30. In various embodiments, the weightpercentage ratio of melamine to methyl gallate ranges from at or between50/50 to 80/20. A shift in the ratio toward increased melamine increasesthe rate of production of smoke during combustion. As such, layers ofvarying ratios could be arranged to create an obscurant device capableof producing varying amounts of smoke over time. In one embodiment, theweight percentage ratio of melamine to methyl gallate is about 50/50. Inone embodiment, the weight percentage ratio of melamine to methylgallate is about 55/45. In one embodiment, the weight percentage ratioof melamine to methyl gallate is about 60/40. In one embodiment, theweight percentage ratio of melamine to methyl gallate is about 65/35. Inone embodiment, the weight percentage ratio of melamine to methylgallate is about 75/25. In one embodiment, the weight percentage ratioof melamine to methyl gallate is about 80/20.

Adding the Binder:

In one embodiment, Applicant's obscurant formulation includes a binder.The addition of a binder allows for the formation of highly denselypacked pellets for use in obscurant devices. In another embodiment,Applicant's obscurant formulation does not include a binder.

The binder is prepared by combining isopropanol and toluene in a flask.The resultant solution is heated and maintained at 60° C. understirring. The ethyl cellulose is added to the solution and stirred untilthe solution returns to 60° C. The powdered smoke formulation/combustioncomponent is slowly added to the solution. The resulting mixture ismixed for approximately 10 to 15 minutes, removed from the heat, pouredinto a dish, and allowed to air dry. The dry mixture is added to amortar and pestle and ground back into a fine powder.

Pressing the Pellets:

A small amount, 0.5 grams, of the powdered smoke formulation/combustioncomponent/binder mixture is added to a 1 inch diameter pellet dye andcompressed using a Carver Press at a pressure of 8,000 pounds for about10 seconds. The compressed pellet is removed from the pellet press. Indifferent embodiments, the pressure to form the pellets is between 1,000pounds to 35,000 pounds. In different embodiments, the pellets are madefrom between 0.5 grams to 20 grams of the mixture. In differentembodiments, the pellets are made from greater than 20 grams of themixture.

The obscurant smoke produced by the pellets upon combustion is nontoxic.Also, all components in Table 1 are biodegradable as is the resultingobscurant smoke. Finally, the pellets burned at a temperature below 350°C., significantly less than red phosphorous, which burns at temperaturesgreater than 500° C.

Referring to FIG. 1, a transmittance graph 100 comparing the lightobscuring performance of various obscurant formulations is depicted. Thegraph was generated from data collected by combusting various obscurantformulations in a 243 cubic inch box with a 7.5 inch width. Light from afluorescent light source was directed across the width of the box to alight detector. The percentage transmittance is represented by they-axis 102. A 100% transmittance value indicates that the light from thesource to the detector is not being hindered. A 0% transmittance valueindicates that no light from the source is reaching the detector. Timeis represented by the x-axis 104.

Lines 110 and 106 represent two different terephthalic acid obscurantformulations. Line 108 represents an embodiment of Applicant's obscurantformulation. Applicant's formulation used in this test comprises a 70/30weight percentage ratio of combustion component to smoke formulation.The smoke formulation comprises a 70/30 ratio of melamine to methylgallate. The 100% transmission value for each line 106, 108, and 110establishes a baseline before each test. As indicated by line 108, thisembodiment of Applicant's melamine/methyl gallate obscurant formulationexhibits superior initial obscuring performance and equivalent obscuringperformance over time.

Referring to FIG. 2, a bar graph 200 of the minimum percenttransmittance (min % T) value for various obscurant formulations isdepicted. The min % T, represented by the y-axis 202, is the lowesttransmittance value recorded in the tests described with respect toFIG. 1. Bars 206 and 208 represent the min % T for two differentterephthalic acid obscurant formulations. Bar 204 represents the min % Tfor Application's melamine/methyl gallate obscurant formulation. Asindicated by bar graph 200, Applicant's formulation exhibits a lower min% T than either terephthalic acid formulations.

Referring to FIG. 3, a bar graph 300 of the values of recovery time to10 percent transmittance (10% T) for various obscurant formulations isdepicted. The 10% T, represented by the y-axis 302, is the time elapsedto reach 10% transmittance in the tests described with respect toFIG. 1. Bars 306 and 308 represent the recovery time to 10% T for twodifferent terephthalic acid obscurant formulations. Bar 304 representsthe recovery time to 10% T for Application's melamine/methyl gallateobscurant formulation. Graph 300 shows that the obscurant smoke producedby Applicant's formulation requires more recovery time to reach 10% Tthan either terephthalic acid formulations.

Referring to FIG. 4, a bar graph of the minimum percentage transmittance(min % T) value for various obscurant formulations, including theindividual components of Applicant's formulation, is depicted. The min %T, represented by the y-axis 402, is the lowest transmittance valuerecorded for each obscurant test. Bar 404 represents the min % T for aterephthalic acid obscurant formulation.

Bar 406 represents the min % T for Application's melamine/methyl gallateobscurant formulation. The embodiment of Applicant's obscurantformulation used in this test comprises a 70/30 wt % ratio ofmelamine/methyl gallate, a potassium chlorate (KClO₃) oxidizercomponent, and a 70/30 wt % ratio of smoke formulation/combustioncomponent. The min % T for Applicant's obscurant formulation issubstantially lower than that of the terephthalic acid obscurantformulation in bar 404, thereby showing that Applicant's formulationproduces a more effective obscurant cloud.

Bar 408 represents the min % T for a melamine obscurant formulation withthe smoke formulation consisting only of melamine. Bar 410 representsthe min % T for a methyl gallate obscurant formulation with the smokeformulation consisting of methyl gallate only. When used alone, theindividual components of one embodiment of Applicant's melamine/methylgallate obscurant formulation, as shown in bars 408 and 410respectively, have a substantially higher min % T value than thecombined melamine/methyl gallate formulation in bar 406.

Bar 412 represents the min % T for a gallic acid (3) obscurantformulation, with the smoke formulation consisting of a mixture ofmelamine and gallic acid. Gallic acid is formed by replacing the methylgroup on methyl gallate with a hydroxyl group.

The min % T of the melamine/methyl gallate obscurant formulationrepresented by bar 406 was substantially lower than that of the gallicacid formulation represented by bar 412.

Bar 414 represents the min % T for a melamine/trimethyl methyl gallate(4) obscurant formulation.

Trimethyl methyl gallate (methyl-3,4,5-trimethoxybenzoate) can besynthesized by dissolving methyl gallate (5.00 g, 27 mmol, 1 equiv.) in150 mL acetone with stirring. Dimethyl sulfate (9.0 mL, 95 mmol, 3.5equiv.) and potassium carbonate (13.70 g, 109 mmol, 4 equiv.) are addedto the reaction, and refluxed for 6 hours. The reaction is filtered, andthe filtrate dried using rotary evaporation. The solid product is mixedwith 100 mL ice water, and then extracted 3 times with 100 mL ethylacetate. The pooled ethyl acetate extract is washed once with 100 mLsaturated NaHCO₃ and once with 100 mL 2 M NH₄OH. The ethyl acetateextract is dried over anhydrous MgSO₄, dried using rotary evaporation,and stored under vacuum overnight.

The min % T of the melamine/methyl gallate obscurant formulationrepresented by bar 406 was substantially lower than that of the gallicacid formulation represented by bar 414.

Referring to FIG. 5, an extinction coefficient graph for obscuring smokeproduced by pyrophoric grenades loaded with various obscurantcompositions is depicted. The tests were conducted by Edgewood ChemicalBiological Center in Edgewood, Md. The x-axis 504 represents wavelengthin μm and the y-axis 502 represents the extinction coefficient inm²/grams.

Line 514 is data from a standard M83 terephthalic acid smoke grenade.The terephthalic acid formulation has a relatively flat extinctioncoefficient profile across the visible spectrum (˜0.38 to ˜0.78 μm) andinto the near infrared spectrum (˜>0.78 μm).

Line 516 is data from one embodiment of Applicant's obscurantformulation prepared according to the components in Table 2.

TABLE 2 Component Type Component Wt. % Combustion Sucrose 12 ComponentPotassium Chlorate (KClO₃) 42 Coolant Magnesium Carbonate (MgCO₃) 6Smoke Melamine 28 Formulation Methyl Gallate 12

The formulation was loaded into a pyrophoric grenade configured to burnfrom one end (end-burn configuration).

Line 512 is data from one embodiment of Applicant's obscurantformulation prepared according to the components in Table 2 loaded intoa pyrophoric grenade configured to burn from the center (core-burnconfiguration).

Line 506 is data from one embodiment of Applicant's obscurantformulation prepared according to the components in Table 3.

TABLE 3 Component Type Component Wt. % Combustion Sucrose 12 ComponentPotassium Chlorate (KClO₃) 30 Coolant Magnesium Carbonate (MgCO₃) 18Smoke Melamine 28 Formulation Methyl Gallate 12

The formulation was loaded into a pyrophoric grenade configured to burnfrom one end (end-burn configuration).

Line 510 is data from one embodiment of Applicant's obscurantformulation prepared according to the components in Table 3 loaded intoa pyrophoric grenade configured to burn from the center (core-burnconfiguration).

Line 508 is data from one embodiment of Applicant's obscurantformulation prepared according to the components in Table 4.

TABLE 4 Component Type Component Wt. % Combustion Sucrose 10 ComponentPotassium Chlorate (KClO₃) 25 Coolant Magnesium Carbonate (MgCO₃) 15Smoke Melamine 35 Formulation Methyl Gallate 15

The formulation was loaded into a pyrophoric grenade configured to burnfrom one end (end-burn configuration).

Line 518 is data from one embodiment of Applicant's obscurantformulation prepared according to the components in Table 4 loaded intoa pyrophoric grenade configured to burn from the center (core-burnconfiguration).

Referring to FIG. 6, an extinction coefficient graph for obscuring smokeproduced by pyrophoric grenades loaded with red phosphorous is depicted.Comparing the red phosphorous lines in FIG. 5 with the linesrepresenting Applicant's formulations in FIG. 4 shows that Applicant'sformulations have superior extinction coefficient values across thetested spectrum in most instances.

Considering the data from FIGS. 5 and 6, the performance of Applicant'sobscurant formulation can be derived. The comparison of Applicant'sformulation against the terephthalic acid (TA) and red phosphorous (RP)formulations are set forth below at 0.55 μm and 0.50 μm, two wavelengthsin the visible spectrum that are of particular interest. The photopiccone cells of the human eye have a maximum sensitivity at 0.55 μm. Thescotopic rod cells of the human eye have a maximum sensitivity at 0.50μm.

TABLE 5 Extinction Coefficient at 0.55 μm extracted from FIGS. 5&6 0.55μm (550 nm) Smoke Extinction Coefficient Formulation (m²/g) TerephthalicAcid 4.85 Red Phosphorus 4.00 Applicant's Formulation 5.11 (Line 508 inFIG. 4)

The extinction coefficient, also known as the mass attenuationcoefficient, is based on the Beer-Lambert Law. The extinctioncoefficient is calculated by:

I=I ₀ e ^(−(μ/p)pl)

Where: I₀ is the original intensity of the beam, I is the intensity ofthe beam at distance l into the substance, e is Euler's number, about2.718, μ is the absorption coefficient, p is the density, (μ/p) is themass attenuation coefficient and pl is the area density, also known asmass thickness.

Using this formula and the data from Table 5, Applicant'smelamine/methyl gallate obscurant formulation at 550 μm exhibits a 1.8fold higher extinction coefficient as compared to the terephthalic acidsmoke and a 12.9 fold higher extinction coefficient as compared to thered phosphorous smoke.

TABLE 6 Extinction Coefficient at 0.50 μm extracted from FIGS. 5&6 0.50μm (500 nm) Smoke Extinction Coefficient Formulation (m²/g) TerephthalicAcid 4.71 Red Phosphorus 4.35 Applicant's Formulation 5.25 (Line 508 inFIG. 4)

Using the extinction coefficient formula above and the data from Table6, Applicant's melamine/methyl gallate obscurant formulation at 0.50 μmexhibits a 3.5 fold higher extinction coefficient as compared to theterephthalic acid smoke and a 7.9 fold higher extinction coefficient ascompared to the red phosphorous smoke.

Referring to FIG. 7, a plot 700 of the thermal aging effect on 0.5 gpellets of Applicant's melamine/methyl gallate obscurant formulation isdepicted. The pellets were stored at 70° C. for up to 10 weeks tosimulate long-term thermal aging. The x-axis 704 represents theequivalent thermal aging time. The y-axis 702 represents the minimum %transmittance for a tested sample. As is shown in the plot 700, nostatistical significant changes in obscurant power were observed due tothermal aging.

Referring to FIGS. 8( a) and 8(b), a ternary plot showing the effect onburn rate of various embodiments of Applicant's obscurant formulationwith varying oxidizer, fuel, and coolant components is depicted. In eachof FIGS. 8( a) and 8(b), axis 802 represents the amount of coolant ineach formulation, axis 804 represents the amount of oxidizer in eachformulation, and axis 810 represents the amount of fuel in eachformulation. The amount of smoke formulation for each test in FIG. 8( a)was held constant while the relative amounts of oxidizer, fuel, andcoolant were varied. Likewise, the amount of smoke formulation for eachtest in FIG. 8( b) was held constant while the relative amounts ofoxidizer, fuel, and coolant were varied, but the ratio of smokeformulation/combustion component was higher in the FIG. 8( b) tests ascompared to the FIG. 8( a) tests.

The burn rate values 806 in seconds/inch are indicated on the plots.Eight burn rate values are shown for FIG. 8( a) and six burn rate valuesare shown for FIG. 8( b). A burn rate of 0 sec/in indicates that theformulation did not ignite. As shown in FIGS. 8( a) and 8(b), a desiredburn rate can be selected by varying the relative amounts of oxidizer,fuel, and coolant. The tests in FIG. 8( a) show burn rates ranging from0-136 sec/in. The tests in FIG. 8( b), where the formulations contain ahigher amount of smoke formulation, show burn rates ranging from 56-110sec/in.

High temperatures will cause the components of the smoke formulation toburn, resulting in undesirable darkening of the produced smoke and adecrease in smoke production. For each of Applicant's testedformulations represented in FIGS. 8( a) and 8(b) that ignited, onlywhite smoke was produced, indicating that burn rates can be successfullyvaried without resulting in undesirable discoloration or decreasedproduction of the obscuring smoke.

In various embodiments, Applicant's two-part smoke formulation comprisesmelamine or a melamine derivative. Referring to FIG. 9, various melaminederivatives for use in various embodiments of Applicant's smokeformulation are depicted. N-imidization of melamine 902 yieldsderivative 904. N-alkylation of melamine 902 yields derivative 906.N-acetylation of melamine 902 yields derivative 908.

Referring to FIG. 10, a polymerization reaction between N-imidization904 and melamine 1002 is depicted. The product 1004 shows the formationof a bond that would result in polymerization if the two reactants areavailable in large quantities. Smoke formulations relying onpolymerization reactions form high molecular weight smoke particulates.

Referring to FIG. 11, various amine-containing melamine derivatives foruse in various embodiments of Applicant's smoke formulation aredepicted. Cyanuric chloride 1102 is reacted with variousamine-containing compounds to introduce functional group substitutes(e.g. aromatic, non-aromatic, and heterocyclic) (see 1104), alcohols(see 1106), carboxylic acids (see 1108), esters, and ethers (see 1110)onto melamine's heterocyclic triazine ring.

In various embodiments, Applicant's smoke formulation comprises melaminederivatives provided in Table 7.

TABLE 7

In various embodiments, Applicant's smoke formulation comprises melaminederivatives formed by a reaction between melamine and an acid anhydride.Acid anhydrides readily acylate melamine. The acid anhydrides include,but are not limited to acetic achydride, trifluoroacetic anhydride,phthalic anhydride, chlorophthalic anhydride, glutaric anhydride, maleicanhydride, fumaric anhydride, chloromaleic anhydride, succinicanhydride, alkyl succinic anhydride, aryl succinic anhydride, benzoicanhydride, mellitic anhydride, pyromellitic dianhydride, oxydiphtalicdianhydride, benzophenone tetracarboxylic dianhydride,hexafluoroisopropylidene anhydride, benzoquinone tetracarboxylicdianhydride, and ethylene tetracarboxylic dianhydride.

In various embodiments, Applicant's smoke formulation comprises aminosubstituted derivatives of melamine. In various embodiments, Applicant'ssmoke formulation comprises amino substituted C—N derivatives ofmelamine, including but not limited to cyanamide, dicyandiamine,ammeline, Ammelide, melem, melon, cyameluric acid, cyanuric acid, andheptazine. In certain embodiments, Applicant's smoke formulationcomprises one or more of the melamine derivatives described in B. Bann &S A Miller “Melamine & Derivatives of Melamine” Chemical Reviews vol 58pp 131-72 (1958), which is incorporated by reference herein.

In various embodiments, Applicant's smoke formulation comprises urea andsubstituted ureas, including but not limited to ethylene urea, methylurea, phenyl urea, diphenyl urea, polysubstituted alkyl, and arylsubstituted ureas.

In various embodiments, Applicant's smoke formulation comprises asubstituted gallate. In various embodiments, the substituted gallatesinclude, but are not limited to, those which have been O-alkylated(aromatic ring hydroxyls have been converted to corresponding etherlinkages) using haloacetic acid and haloacetic acid esters (e.g.chloroacetic, methyl chloroacetate, ethyl chloroacetate, bromoacetic,and methyl bromoacetate). In various embodiments, the substitutedgallates include those which have been O-alkylated using dimethylsulfate, diethyl sulfate, benzyl chloride, or benzyl bromide.

In various embodiments, Applicant's smoke formulation comprises gallicacid derivatives including but not limited to gallic acid and its salts,methyl gallate, ethyl gallate, propyl gallate, octyl gallate, dodecylgallate, gallocatechin gallate, epicatechin gallate, gallamide, alkyland aryl substituted gallamide derivatives, and mono, di andtri-substituted hydroxybenzoic acid derivatives.

In one embodiment, Applicant's smoke formulation comprises a mixture ofmelamine, methyl gallate, and terephthalic acid.

In one embodiment, Applicant's smoke formulation comprises an imide,including but not limited to succinimide, maleimide, adipimide,phthalimide, diphenyl imide, naphthalimide, glutarimide and a gallateester. In one embodiment, Applicant's smoke formulation comprises animide and melamine. In one embodiment, Applicant's smoke formulationcomprises an imide, melamine, and a gallate ester.

In various embodiments, Applicant's smoke formulation comprises abisphenol derivative. In different embodiments, the bisphenol derivativeis, without limitation, Bisphenol A (BPA), Bisphenol F, Bisphenol S(BPS), Bisphenol E, Bisphenol B, Bisphenol P, Bisphenol PH, BisphenolBP, Bisphenol AF, Bisphenol AP, Bisphenol C, Bisphenol E, Bisphenol G,Bisphenol M, Bisphenol TMC, Bisphenol Z, hydroxybenzophenone,dihydroxybenzophenone, hydroxyacetophenone or a combination thereof. Insome embodiments, Applicant's smoke formulation comprises a bisphenolderivative and melamine. In some embodiments, Applicant's smokeformulation comprises a bisphenol derivative and methyl gallate. In someembodiments, Applicant's smoke formulation comprises a bisphenolderivative, melamine, and methyl gallate.

In various embodiments, Applicant's smoke formulation comprisespolyphenolic derivatives including but not limited to ellagic acid,triphenol, trishydroxyphenyl ethane, phL dihydroxyphenyl acetic acid andits salts, dihydroxyphenyl propionic acid and its salts, phloroglucinol,gallocatechin or epigallocatechin, or a combination thereof. In someembodiments, Applicant's smoke formulation comprises a polyphenolicderivative and melamine. In some embodiments, Applicant's smokeformulation comprises a polyphenolic derivative and methyl gallate. Insome embodiments, Applicant's smoke formulation comprises a polyphenolicderivative, melamine, and methyl gallate.

Provided below are examples of compounds included in various embodimentsof Applicant's smoke formulation:

In various embodiments, Applicant's smoke formulation comprises one ofmore of the bisphenol derivatives and dicarboxylic acids presented inTable 8.

TABLE 8

The following Examples are presented to further illustrate to personsskilled in the art how to make and use the invention. The Examples arenot intended as a limitation, however, upon the scope of Applicant'sinvention.

Example 2

In one embodiment, an obscurant formulation having a smoke componentconsisting of melamine, methyl gallate, and 1 weight % sebacic acid isprepared according to Table 9.

TABLE 9 1% Sebacic Acid Formulation Component Type Component Wt. %Quantity (g) Combustion Sucrose 38.1 3.81 Component Potassium Chlorate38.1 3.81 Smoke Melamine 15.2 1.52 Formulation Methyl Gallate 6.5 0.65Sebacic Acid 1.00 0.10 Binder Ethyl Cellulose 1.00 0.10

Example 3

In one embodiment, an obscurant formulation having a smoke componentconsisting of melamine, methyl gallate, and 5 weight % sebacic acid isprepared according to Table 10.

TABLE 10 5% Sebacic Acid Formulation Component Type Component Wt. %Quantity (g) Combustion Sucrose 38.1 3.81 Component Potassium Chlorate38.1 3.81 Smoke Melamine 12.4 1.24 Formulation Methyl Gallate 5.3 0.53Sebacic Acid 5.00 0.50 Binder Ethyl Cellulose 1.00 0.10

Example 4

In one embodiment, an obscurant formulation having a smoke componentconsisting of melamine, methyl gallate, and 1 weight % adipic acid isprepared according to Table 11.

TABLE 11 1% Adipic Acid Formulation Component Type Component Wt. %Quantity (g) Combustion Sucrose 37.7 3.77 Component Potassium Chlorate37.7 3.77 Smoke Melamine 15.8 1.58 Formulation Methyl Gallate 6.8 0.68Adipic Acid 1.00 0.10 Binder Ethyl Cellulose 1.00 0.10

Example 5

In one embodiment, an obscurant formulation having a smoke componentconsisting of melamine, methyl gallate, and 5 weight % adipic acid isprepared according to Table 12.

TABLE 12 5% Adipic Acid Formulation Component Type Component Wt. %Quantity (g) Combustion Sucrose 38.1 3.81 Component Potassium Chlorate38.1 3.81 Smoke Melamine 12.4 1.24 Formulation Methyl Gallate 5.3 0.53Adipic Acid 5.00 0.50 Binder Ethyl Cellulose 1.00 0.10

Example 6

In one embodiment, an obscurant formulation having a smoke componentconsisting of melamine, methyl gallate, and 1 weight % azelaic acid isprepared according to Table 13.

TABLE 13 1% Azelaic Acid Formulation Component Type Component Wt. %Quantity (g) Combustion Sucrose 38.1 3.81 Component Potassium Chlorate38.1 3.81 Smoke Melamine 15.2 1.52 Formulation Methyl Gallate 6.5 0.65Azelaic Acid 1.00 0.10 Binder Ethyl Cellulose 1.00 0.10

Example 7

In one embodiment, an obscurant formulation having a smoke componentconsisting of melamine, methyl gallate, and 5 weight % azelaic acid isprepared according to Table 14.

TABLE 14 5% Azelaic Acid Formulation Component Type Component Wt. %Quantity (g) Combustion Sucrose 38.1 3.81 Component Potassium Chlorate38.1 3.81 Smoke Melamine 12.4 1.24 Formulation Methyl Gallate 5.3 0.53Azelaic Acid 5.00 0.50 Binder Ethyl Cellulose 1.00 0.10

Example 8

In one embodiment, an obscurant formulation having a smoke componentconsisting of melamine, methyl gallate, and 1 weight % dimethylsulfoneis prepared according to Table 15.

TABLE 15 1% Dimethylsulfone Formulation Component Type Component Wt. %Quantity (g) Combustion Sucrose 38.1 3.81 Component Potassium Chlorate38.1 3.81 Smoke Melamine 15.2 1.52 Formulation Methyl Gallate 6.5 0.65Dimethylsulfone 1.00 0.10 Binder Ethyl Cellulose 1.00 0.10

Example 9

In one embodiment, an obscurant formulation having a smoke componentconsisting of melamine, methyl gallate, and 5 weight % azelaic acid isprepared according to Table 16.

TABLE 16 5% Dimethylsulfone Formulation Component Type Component Wt. %Quantity (g) Combustion Sucrose 38.1 3.81 Component Potassium Chlorate38.1 3.81 Smoke Melamine 12.4 1.24 Formulation Methyl Gallate 5.3 0.53Dimethylsulfone 5.00 0.50 Binder Ethyl Cellulose 1.00 0.10

Example 10

In one embodiment, an obscurant formulation having a smoke componentconsisting of melamine, methyl gallate, and 1 weight % Bisphenol S isprepared according to Table 17.

TABLE 17 1% Bisphenol S Formulation Component Type Component Wt. %Quantity (g) Combustion Sucrose 38.1 3.81 Component Potassium Chlorate38.1 3.81 Smoke Melamine 15.2 1.52 Formulation Methyl Gallate 6.5 0.65Bisphenol S 1.00 0.10 Binder Ethyl Cellulose 1.00 0.10

Example 11

In one embodiment, an obscurant formulation having a smoke componentconsisting of melamine, methyl gallate, and 5 weight % Bisphenol S isprepared according to Table 18.

TABLE 18 5% Bisphenol S Formulation Component Type Component Wt. %Quantity (g) Combustion Sucrose 38.1 3.81 Component Potassium Chlorate38.1 3.81 Smoke Melamine 12.4 1.24 Formulation Methyl Gallate 5.3 0.53Bisphenol S 5.00 0.50 Binder Ethyl Cellulose 1.00 0.10

Example 12

In one embodiment, an obscurant formulation having a smoke componentconsisting of melamine, methyl gallate, and 1 weight % Bisphenol A isprepared according to Table 19.

TABLE 19 1% Bisphenol A Formulation Component Type Component Wt. %Quantity (g) Combustion Sucrose 38.1 3.81 Component Potassium Chlorate38.1 3.81 Smoke Melamine 15.2 1.52 Formulation Methyl Gallate 6.5 0.65Bisphenol A 1.00 0.10 Binder Ethyl Cellulose 1.00 0.10

Example 13

In one embodiment, an obscurant formulation having a smoke componentconsisting of melamine, methyl gallate, and 5 weight % Bisphenol A isprepared according to Table 20.

TABLE 20 5% Bisphenol A Formulation Component Type Component Wt. %Quantity (g) Combustion Sucrose 38.1 3.81 Component Potassium Chlorate38.1 3.81 Smoke Melamine 12.4 1.24 Formulation Methyl Gallate 5.3 0.53Bisphenol A 5.00 0.50 Binder Ethyl Cellulose 1.00 0.10

Example 14

In one embodiment, an obscurant formulation having a smoke componentconsisting of melamine and THEIC is prepared according to Table 21.

TABLE 21 THEIC Formulation Component Type Component Wt. % Quantity (g)Combustion Sucrose 38.1 3.81 Component Potassium Chlorate 38.1 3.81Smoke Melamine 15.9 1.59 Formulation THEIC 6.80 0.68 Binder EthylCellulose 1.00 0.10

Example 15

In one embodiment, an obscurant formulation having a smoke componentconsisting of melamine and 5-methoxy methyl gallate is preparedaccording to Table 22.

TABLE 22 5-Methoxy Methyl Gallate Formulation Component Type ComponentWt. % Quantity (g) Combustion Sucrose 38.1 3.81 Component PotassiumChlorate 38.1 3.81 Smoke Melamine 15.9 1.59 Formulation 5-Methoxy MethylGallate 6.80 0.68 Binder Ethyl Cellulose 1.00 0.10

Example 16

In one embodiment, an obscurant formulation having a smoke componentconsisting of melamine and dimethylsulfone is prepared according toTable 23.

TABLE 23 Melamine/Dimethylsulfone Formulation Component Type ComponentWt. % Quantity (g) Combustion Sucrose 38.1 3.81 Component PotassiumChlorate 38.1 3.81 Smoke Melamine 15.9 1.59 Formulation Dimethylsulfone6.80 0.68 Binder Ethyl Cellulose 1.00 0.10

Example 17

In one embodiment, an obscurant formulation having a smoke componentconsisting of methyl gallate and dimethylsulfone is prepared accordingto Table 24.

TABLE 24 Methyl Gallate/Dimethylsulfone Formulation Component TypeComponent Wt. % Quantity (g) Combustion Sucrose 38.1 3.81 ComponentPotassium Chlorate 38.1 3.81 Smoke Methyl Gallate 6.80 0.68 FormulationDimethylsulfone 15.9 1.59 Binder Ethyl Cellulose 1.00 0.10

Example 18

In one embodiment, an obscurant formulation having a smoke componentconsisting of melamine and Bisphenol A is prepared according to Table25.

TABLE 25 Melamine/Bisphenol A Formulation Component Type Component Wt. %Quantity (g) Combustion Sucrose 38.1 3.81 Component Potassium Chlorate38.1 3.81 Smoke Melamine 15.9 1.59 Formulation Bisphenol A 6.80 0.68Binder Ethyl Cellulose 1.00 0.10

Example 19

In one embodiment, an obscurant formulation having a smoke componentconsisting of methyl gallate and Bisphenol A is prepared according toTable 26.

TABLE 26 Methyl Gallate/Bisphenol A Formulation Component Type ComponentWt. % Quantity (g) Combustion Sucrose 38.1 3.81 Component PotassiumChlorate 38.1 3.81 Smoke Methyl Gallate 6.9 0.69 Formulation Bisphenol A15.9 1.59 Binder Ethyl Cellulose 1.00 0.10

Example 20

In one embodiment, an obscurant formulation having a smoke componentconsisting of melamine and Bisphenol A is prepared according to Table27.

TABLE 27 Melamine/Bisphenol S Formulation Component Type Component Wt. %Quantity (g) Combustion Sucrose 38.1 3.81 Component Potassium Chlorate38.1 3.81 Smoke Melamine 15.9 1.59 Formulation Bisphenol S 6.80 0.68Binder Ethyl Cellulose 1.00 0.10

Example 21

In one embodiment, an obscurant formulation having a smoke componentconsisting of methyl gallate and Bisphenol A is prepared according toTable 28.

TABLE 28 Methyl Gallate/Bisphenol S Formulation Component Type ComponentWt. % Quantity (g) Combustion Sucrose 38.1 3.81 Component PotassiumChlorate 38.1 3.81 Smoke Methyl Gallate 6.8 0.68 Formulation Bisphenol S15.9 1.59 Binder Ethyl Cellulose 1.00 0.10

Referring to FIG. 13, a bar graph 1300 of the minimum percenttransmittance (min % T) values for the obscurant formulations presentedin Examples 2-7 is depicted. The min % T, represented by the y-axis1302, is the lowest transmittance value recorded in testing for eachobscurant formulation. The obscurant formulation for each bar isidentified on the x-axis 1304. Bar 1306 represents the min % T for theobscurant formulation with a 70/30 weight percentage ratio ofmelamine/methyl gallate and a 77/23 weight percentage of propellant andbinder/smoke formulation. Bar 1308 represents the min % T for theobscurant formulation containing melamine, methyl gallate, and 1% adipicacid according to Example 4. Bar 1310 represents the min % T for theobscurant formulation containing melamine, methyl gallate, and 5% adipicacid according to Example 5. Bar 1312 represents the min % T for theobscurant formulation containing melamine, methyl gallate, and 1%azelaic acid according to Example 6. Bar 1314 represents the min % T forthe obscurant formulation containing melamine, methyl gallate, and 5%azelaic acid according to Example 7. Bar 1316 represents the min % T forthe obscurant formulation containing melamine, methyl gallate, and 1%sebacic acid according to Example 2. Bar 1318 represents the min % T forthe obscurant formulation containing melamine, methyl gallate, and 5%sebacic acid according to Example 3.

Referring to FIG. 14, a bar graph 1400 of the values of recovery time to10 percent transmittance (10% T) for the obscurant formulationspresented in Examples 2-7 is depicted. The 10% T values, represented bythe y-axis 1402, is the time elapsed to reach 10% in testing for eachobscurant formulation. The obscurant formulation for each bar isidentified on the x-axis 1404. Bar 1406 represents the 10% T for theobscurant formulation with a 70/30 weight percentage ratio ofmelamine/methyl gallate and a 77/23 weight percentage of propellant andbinder/smoke formulation. Bar 1408 represents the 10% T for theobscurant formulation containing melamine, methyl gallate, and 1% adipicacid according to Example 4. Bar 1410 represents the 10% T for theobscurant formulation containing melamine, methyl gallate, and 5% adipicacid according to Example 5. Bar 1412 represents the 10% T for theobscurant formulation containing melamine, methyl gallate, and 1%azelaic acid according to Example 6. Bar 1414 represents the 10% T forthe obscurant formulation containing melamine, methyl gallate, and 5%azelaic acid according to Example 7. Bar 1416 represents the 10% T forthe obscurant formulation containing melamine, methyl gallate, and 1%sebacic acid according to Example 2. Bar 1418 represents the 10% T forthe obscurant formulation containing melamine, methyl gallate, and 5%sebacic acid according to Example 3.

The data from the tests depicted in FIGS. 13 and 14 is summarized inTable 26:

TABLE 26 Comparison of Melamine/Methyl Gallate Obscurant to theFormulations in Examples 2-7. 1% Melamine/ Adipic 5% Adipic 1% Azelaic5% Azelaic 1% Sebacic 5% Sebacic MeGallate Acid Acid Acid Acid Acid AcidMin % T 1.6 1.7 2.4 1.2 2.3 5.8 3.1 Std Dev 0.5 0.5 0.5 0.5 0.8 2.7 0.4P-value N/A 0.618 0.045 0.157 0.158 0.052 0.001 Time <10% T 192.7 176.4115.5 153.8 137.5 73.5 120.5 Std Dev 26.8 35.2 11.8 18.6 11.3 53.2 15.9P-value N/A 0.441 0.000 0.009 0.000 0.016 0.000

Referring to FIG. 15, a bar graph 1500 of the minimum percenttransmittance (min % T) values for the obscurant formulations presentedin Examples 8, 9, 16, and 17 is depicted. The min % T, represented bythe y-axis 1502, is the lowest transmittance value recorded in testingfor each obscurant formulation. The obscurant formulation for each baris identified on the x-axis 1504. Bar 1506 represents the min % T forthe obscurant formulation with a 70/30 weight percentage ratio ofmelamine/methyl gallate and a 77/23 weight percentage of propellant andbinder/smoke formulation. Bar 1508 represents the min % T for theobscurant formulation containing melamine and dimethylsulfone accordingto Example 16. Bar 1510 represents the min % T for the obscurantformulation containing methyl gallate and dimethylsulfone according toExample 17. Bar 1512 represents the min % T for the obscurantformulation containing melamine, methyl gallate, and 1% dimethylsulfoneaccording to Example 8. Bar 1514 represents the min % T for theobscurant formulation containing melamine, methyl gallate, and 5%dimethylsulfone according to Example 9.

Referring to FIG. 16, a bar graph 1600 of the values of recovery time to10 percent transmittance (10% T) for the obscurant formulationspresented in Examples 8, 9, 16, and 17 is depicted. The 10% T values,represented by the y-axis 1602, is the time elapsed to reach 10% intesting for each obscurant formulation. The obscurant formulation foreach bar is identified on the x-axis 1604. Bar 1606 represents the 10% Tfor the obscurant formulation with a 70/30 weight percentage ratio ofmelamine/methyl gallate and a 77/23 weight percentage of propellant andbinder/smoke formulation. Bar 1608 represents the 10% T for theobscurant formulation containing melamine and dimethylsulfone accordingto Example 16. Bar 1610 represents the 10% T for the obscurantformulation containing methyl gallate and dimethylsulfone according toExample 17. Bar 1612 represents the 10% T for the obscurant formulationcontaining melamine, methyl gallate, and 1% dimethylsulfone according toExample 8. Bar 1614 represents the 10% T for the obscurant formulationcontaining melamine, methyl gallate, and 5% dimethylsulfone according toExample 9.

The data from the tests depicted in FIGS. 15 and 16 is summarized inTable 27:

TABLE 27 Comparison of Melamine/Methyl Gallate Obscurant to theFormulations in Examples 8, 9, 16 and 17. Melamine/ Dimethyl- 1% 5%Melamine/ Dimethyl- sulfone/ Dimethyl- Dimethyl- MeGallate sulfoneMeGallate sulfone sulfone Min % T 1.6 10.5 24.1 2.6 3.2 Std Dev 0.5 1.46.5 0.5 1.3 P-value N/A 0.001 0.006 0.008 0.092 Time <10% 192.7 0.0 5.8150.8 134.0 T Std Dev 26.8 0.0 11.5 20.8 39.8 P-value N/A 0.000 0.0000.008 0.051

Referring to FIG. 17, a bar graph 1700 of the minimum percenttransmittance (min % T) values for the obscurant formulations presentedin Examples 10, 11, 20, and 21 is depicted. The min % T, represented bythe y-axis 1702, is the lowest transmittance value recorded in testingfor each obscurant formulation. The obscurant formulation for each baris identified on the x-axis 1704. Bar 1706 represents the min % T forthe obscurant formulation with a 70/30 weight percentage ratio ofmelamine/methyl gallate and a 77/23 weight percentage of propellant andbinder/smoke formulation. Bar 1508 represents the min % T for theobscurant formulation containing melamine and Bisphenol S according toExample 20. Bar 1510 represents the min % T for the obscurantformulation containing methyl gallate and Bisphenol S according toExample 21. Bar 1512 represents the min % T for the obscurantformulation containing melamine, methyl gallate, and 1% Bisphenol Saccording to Example 10. Bar 1514 represents the min % T for theobscurant formulation containing melamine, methyl gallate, and 5%Bisphenol S according to Example 11.

Referring to FIG. 18, a bar graph 1800 of the values of recovery time to10 percent transmittance (10% T) for the obscurant formulationspresented in Examples 10, 11, 20, and 21 is depicted. The 10% T values,represented by the y-axis 1802, is the time elapsed to reach 10% intesting for each obscurant formulation. The obscurant formulation foreach bar is identified on the x-axis 1804. Bar 1806 represents the 10% Tfor the obscurant formulation with a 70/30 weight percentage ratio ofmelamine/methyl gallate and a 77/23 weight percentage of propellant andbinder/smoke formulation. Bar 1808 represents the 10% T for theobscurant formulation containing melamine and Bisphenol S according toExample 20. Bar 1810 represents the 10% T for the obscurant formulationcontaining methyl gallate and Bisphenol S according to Example 21. Bar1812 represents the 10% T for the obscurant formulation containingmelamine, methyl gallate, and 1% Bisphenol S according to Example 10.Bar 1814 represents the 10% T for the obscurant formulation containingmelamine, methyl gallate, and 5% Bisphenol S according to Example 11.

The data from the tests depicted in FIGS. 17 and 18 is summarized inTable 28:

TABLE 28 Comparison of Melamine/Methyl Gallate Obscurant to theFormulations in Examples 10, 11, 21 and 22. Melamine/ Melamine/ BPS/ 1%Bis- 5% Bis- MeGallate BPS MeGallate phenol S phenol S Min % T 1.6 3.30.8 2.5 1.1 Std Dev 0.5 1.0 0.1 0.9 0.3 P-value N/A 0.016 0.001 0.0930.058 Time <10% 192.7 131.4 505.8 187.0 232.6 T Std Dev 26.8 26.4 6.423.5 17.2 P-value N/A 0.003 0.000 0.713 0.006

Referring to FIG. 19, a bar graph 1900 of the minimum percenttransmittance (min % T) values for the obscurant formulations presentedin Examples 8, 9, 16, and 17 is depicted. The min % T, represented bythe y-axis 1902, is the lowest transmittance value recorded in testingfor each obscurant formulation. The obscurant formulation for each baris identified on the x-axis 1904. Bar 1906 represents the min % T forthe obscurant formulation with a 70/30 weight percentage ratio ofmelamine/methyl gallate and a 77/23 weight percentage of propellant andbinder/smoke formulation. Bar 1908 represents the min % T for theobscurant formulation containing melamine and dimethylsulfone accordingto Example 8. Bar 1910 represents the min % T for the obscurantformulation containing methyl gallate and dimethylsulfone according toExample 9. Bar 1912 represents the min % T for the obscurant formulationcontaining melamine, methyl gallate, and 1% dimethylsulfone according toExample 16. Bar 1914 represents the min % T for the obscurantformulation containing melamine, methyl gallate, and 5% dimethylsulfoneaccording to Example 17.

Referring to FIG. 20, a bar graph 2000 of the values of recovery time to10 percent transmittance (10% T) for the obscurant formulationspresented in Examples 8, 9, 16, and 17 is depicted. The 10% T values,represented by the y-axis 2002, is the time elapsed to reach 10% intesting for each obscurant formulation. The obscurant formulation foreach bar is identified on the x-axis 2004. Bar 2006 represents the 10% Tfor the obscurant formulation with a 70/30 weight percentage ratio ofmelamine/methyl gallate and a 77/23 weight percentage of propellant andbinder/smoke formulation. Bar 2008 represents the 10% T for theobscurant formulation containing melamine and dimethylsulfone accordingto Example 8. Bar 2010 represents the 10% T for the obscurantformulation containing methyl gallate and dimethylsulfone according toExample 9. Bar 2012 represents the 10% T for the obscurant formulationcontaining melamine, methyl gallate, and 1% dimethylsulfone according toExample 16. Bar 2014 represents the 10% T for the obscurant formulationcontaining melamine, methyl gallate, and 5% dimethylsulfone according toExample 17.

The data from the tests depicted in FIGS. 19 and 20 is summarized inTable 29:

TABLE 29 Comparison of Melamine/Methyl Gallate Obscurant to theFormulations in Examples 8, 9, 16, and 17. Melamine/ Diphenyl- 1% 5%Melamine/ Diphenyl- sulfone/ Diphenyl- Diphenyl- MeGallate sulfoneMeGallate sulfone sulfone Min % T 1.6 20.1 13.1 1.1 1.2 Std Dev 0.5 4.23.7 1.0 0.4 P-value N/A 0.003 0.008 0.362 0.140 Time <10% 192.7 0.0 5.3197.4 146.5 T Std Dev 26.8 0.0 10.5 38.3 11.4 P-value N/A 0.000 0.0000.814 0.001

Referring to FIG. 21, a bar graph 2100 of the minimum percenttransmittance (min % T) values for the obscurant formulations presentedin Examples 12, 13, 18, and 19 is depicted. The min % T, represented bythe y-axis 2102, is the lowest transmittance value recorded in testingfor each obscurant formulation. The obscurant formulation for each baris identified on the x-axis 2104. Bar 2106 represents the min % T forthe obscurant formulation with a 70/30 weight percentage ratio ofmelamine/methyl gallate and a 77/23 weight percentage of propellant andbinder/smoke formulation. Bar 2108 represents the min % T for theobscurant formulation containing melamine and Bisphenol A according toExample 18. Bar 2110 represents the min % T for the obscurantformulation containing methyl gallate and Bisphenol A according toExample 19. Bar 2112 represents the min % T for the obscurantformulation containing melamine, methyl gallate, and 1% Bisphenol Aaccording to Example 12. Bar 2114 represents the min % T for theobscurant formulation containing melamine, methyl gallate, and 5%Bisphenol A according to Example 13.

Referring to FIG. 22, a bar graph 2200 of the values of recovery time to10 percent transmittance (10% T) for the obscurant formulationspresented in Examples 12, 13, 18, and 19 is depicted. The 10% T values,represented by the y-axis 2202, is the time elapsed to reach 10% intesting for each obscurant formulation. The obscurant formulation foreach bar is identified on the x-axis 2204. Bar 2206 represents the 10% Tfor the obscurant formulation with a 70/30 weight percentage ratio ofmelamine/methyl gallate and a 77/23 weight percentage of propellant andbinder/smoke formulation. Bar 2208 represents the 10% T for theobscurant formulation containing melamine and Bisphenol A according toExample 18. Bar 2210 represents the 10% T for the obscurant formulationcontaining methyl gallate and Bisphenol A according to Example 19. Bar2212 represents the 10% T for the obscurant formulation containingmelamine, methyl gallate, and 1% Bisphenol A according to Example 12.Bar 2214 represents the 10% T for the obscurant formulation containingmelamine, methyl gallate, and 5% Bisphenol A according to Example 13.

The data from the tests depicted in FIGS. 19 and 20 is summarized inTable 30:

TABLE 30 Comparison of Melamine/Methyl Gallate Obscurant to theFormulations in Examples 12, 13, 18, and 19. Melamine/ Melamine/ BPA/ 1%Bis- 5% Bis- MeGallate BPA MeGallate phenol A phenol A Min % T 1.6 6.60.8 0.6 Std Dev 0.5 0.8 0.3 0.6 P-value N/A 0.000 0.003 0.011 Time <10%192.7 45.8 410.0 203.0 T Std Dev 26.8 13.4 35.9 28.7 P-value N/A 0.0000.000 0.527

Referring to FIG. 23, a bar graph 2300 of the minimum percenttransmittance (min % T) values for the obscurant formulations presentedin Examples 14 and 15 is depicted. The min % T, represented by they-axis 2302, is the lowest transmittance value recorded in testing foreach obscurant formulation. The obscurant formulation for each bar isidentified on the x-axis 2304. Bar 2306 represents the min % T for theobscurant formulation with a 70/30 weight percentage ratio ofmelamine/methyl gallate and a 77/23 weight percentage of propellant andbinder/smoke formulation. Bar 2108 represents the min % T for theobscurant formulation containing melamine and 5-methoxy methyl gallateaccording to Example 15. Bar 2110 represents the min % T for theobscurant formulation containing melamine and THEIC according to Example14.

Referring to FIG. 24, a bar graph 2400 of the values of recovery time to10 percent transmittance (10% T) for the obscurant formulationspresented in Examples 14 and 15 is depicted. The 10% T values,represented by the y-axis 2402, is the time elapsed to reach 10% intesting for each obscurant formulation. The obscurant formulation foreach bar is identified on the x-axis 2404. Bar 2406 represents the 10% Tfor the obscurant formulation with a 70/30 weight percentage ratio ofmelamine/methyl gallate and a 77/23 weight percentage of propellant andbinder/smoke formulation. Bar 2408 represents the 10% T for theobscurant formulation containing melamine and 5-methoxy methyl gallateaccording to Example 15. Bar 2410 represents the 10% T for the obscurantformulation containing melamine and THEIC according to Example 14.

The data from the tests depicted in FIGS. 23 and 24 is summarized inTable 31:

TABLE 31 Comparison of Melamine/Methyl Gallate Obscurant to theFormulations in Examples 14 and 15. Melamine/ 5-Methoxy MeGallateMeGallate THEIC Min % T 1.6 4.9 7.9 Std Dev 0.5 2.3 1.3 P-value N/A0.065 0.002 Time <10% T 192.7 73.8 28.5 Std Dev 26.8 36.3 13.4 P-valueN/A 0.003 0.000

In some embodiments, Applicant's obscurant formulation comprises oxamideor a oximide derivative. In some embodiment, Applicant's obscurantformulation comprises a 1:1 molar condensation product between diethyloxalate and ethylene diamine. In one embodiment, the condensationproduct comprises a mixture of ethylene oxamide cyclics and polyethyleneoxamide oligomers as shown in (I).

In one embodiment, Applicant's smoke formulation comprises thecondensation product from (I) and methyl gallate. In one embodiment,Applicant's obscurant formulation comprises the condensation productfrom (I) and a sucrose/alkali chlorate propellant.

In one embodiment, a polyethylene oxamide oligomer is prepared by addingdiethyl oxalate dropwise with stirring to a solution of ethylene diaminein a toluene solvent at room temperature. The solution is stirred for 30minutes followed by filtering off the white polyethylene oxamideprecipitate. The precipitate is vacuum dried to remove residual solventand is then blended with methyl gallate. In one embodiment, the ratio ofethylene oxamide to methyl gallate is determined by the melamine/methylgallate mixtures descried herein, except that an equimolar amount ofethylene oxamide is substituted for the melamine.

In various embodiments, Applicant's smoke formulation comprises boron,boron carbide, boron nitride, titanium hydride powder, or a combinationthereof. In various embodiments, Applicant's smoke formulation comprisesmethyl gallate combined with boron, boron carbide, boron nitride,titanium hydride powder, or a combination thereof.

In one embodiment, Applicant's smoke formulation comprises alkyleneoxamide and methyl gallate. In one embodiment, Applicant's obscurantformulation comprises alkylene oxamide and a sucrose/alkali chloratepropellant.

In various embodiments, the propellant of Applicant's obscurantformulation comprises sucrose, lactose, glucose, fructose, sorbitol,threose, erythritol, pentaerythritol, or a combination thereof. In otherembodiments, Applicant's obscurant formulation comprises any compoundknown to be capable of readily oxidizing and, in the presence of astrong oxidizer, capable of generating sufficient heat to vaporize thesmoke formulation.

In one embodiment, Applicant's obscurant formulation comprises acoolant. In one embodiment, Applicant's obscurant formulation does notinclude a coolant. In one embodiment, the coolant comprises MgCO₃. Inone embodiment, the coolant comprises NaHCO₃.

In one embodiment, Applicant's formulation does not include a binder. Inone embodiment, Applicant's formulation includes a binder. In oneembodiment, the binder includes Citroflex, a plasticizer sold incommerce by Vertellus Specialties, Inc., which results in pellets thatare generally easier to press than non-plasticized formulations. In oneembodiment, the binder comprises nitrocellulose. In one embodiment, thebinder comprises ethylcellulose.

Referring to FIG. 12, an exemplary method of preparing an obscurantdevice capable of producing obscurant smoke at various rates isdepicted. The method begins at step 1202. An obscurant formulation witha burn rate of 136 sec/in is prepared at step 1204. An obscurantformulation with a burn rate of 24 sec/in is prepared at step 1206. The136 sec/in formulation is pressed into the form of a cylinder to form acore at step 1208. The 24 sec/in formulation is pressed into a cylinderaround the 136 sec/in core to form a concentric cylinder at step 1210. Afuse is inserted into the concentric cylinder at step 1212. Theconcentric cylinder is loaded into an obscurant device housing at step1214. In various embodiments, the obscurant device housing is a smokegrenade, an obscurant rocket, or other type of obscurant artillery. Themethod ends at step 1216.

When the obscurant device is triggered and the fuse ignited, the innerportion of the concentric cylinder, containing the 136 sec/in obscurantformulation burns, producing a dense obscurant smoke (i.e., the highburn rate results in higher smoke production). Once the inner portion ofthe concentric cylinder fully combusts, the outer portion of theconcentric cylinder burns, producing a lower density obscurant smoke(i.e., the lower burn rate results in a lower rate of smoke production).This dual-burn rate configuration can produce a heavy initial smokescreen followed by a sustaining smoke screen to maintain the obscuranteffect for a longer period of time as compared to single-burn rateconfigurations. In different embodiments, the device contains 3 or morelayers of obscurant formulations, each with a different burn rate. Whilethe exemplary method described in FIG. 12 includes obscurantformulations with 136 and 24 sec/in burn rates, different formulationsand combinations of formulations of Applicant's obscurant (withdifferent burn rates) may be used as necessary for different purposes.

In addition to military applications, a formulation capable of producingnontoxic smoke at a low burn temperature has application in the civilianrealm. For example, smoke precursors may be used for detecting leakswithin heating ventilation and air conditioning (HVAC) systems. Aductwork test is typically performed after the initial installation ofeach new HVAC system. Periodic testing after installation is alsodesirable. In various embodiments, the smoke produced by Applicant'snontoxic melamine-based, low burn temperature formulations describedherein is directed into the ductwork of a HVAC system. The high densitysmoke flows through the ductwork and out any openings, therebyidentifying any leaks in the system.

While specific values have been recited for the various embodimentsrecited herein, it is to be understood that, within the scope of theinvention, the values of all parameters, including amounts and ratios,may vary over wide ranges to suit different applications.

While the invention is described through the above-described exemplaryembodiments, it will be understood by those of ordinary skill in the artthat modifications to, and variations of, the illustrated embodimentsmay be made without departing from the inventive concepts disclosedherein. For example, although some aspects have been described withreference to a flowchart, those skilled in the art should readilyappreciate that functions, operations, decisions, etc. of all or aportion of each block, or a combination of blocks, of the flowchart maybe combined, separated into separate operations or performed in otherorders. In addition, although a obscurant has been described, thedisclosed methods and formulations may be used for other purposes,including location marking, special effects, and included in pyrotechnicdisplays. Furthermore, disclosed aspects, or portions of these aspects,may be combined in ways not listed above. Accordingly, the inventionshould not be viewed as being limited to the disclosed embodiment(s).

1. A composition to produce smoke upon combustion, comprising: acombustion component; and a smoke formulation.
 2. The composition ofclaim 1, wherein said smoke formulation comprises a gallate ester. 3.The composition of claim 2, wherein said smoke formulation furthercomprises melamine.
 4. The composition of claim 3, wherein said smokeformulation further comprises a polyphenolic derivative.
 5. Thecomposition of claim 3, wherein said smoke formulation further comprisesa dicarboxylic acid.
 6. The composition of claim 3, wherein said smokeformulation further comprises an imide.
 7. The composition of claim 2,wherein said smoke formulation comprises bisphenol S.
 8. The compositionof claim 7, wherein said smoke formulation further comprises melamine.9. The composition of claim 2, wherein said smoke formulation comprisesbisphenol A.
 10. The composition of claim 9, wherein said smokeformulation further comprises melamine.
 11. The composition of claim 2,wherein said smoke formulation comprises diemthylsulfone.
 12. Thecomposition of claim 11, wherein said smoke formulation furthercomprises melamine.
 13. The composition of claim 1, wherein said smokeformulation comprises melamine.
 14. The composition of claim 13, whereinsaid smoke formulation further comprises THEIC.
 15. The composition ofclaim 13, wherein said smoke formulation further comprises an oxamide.16. The composition of claim 13, wherein said smoke formulation furthercomprises an imide.
 17. The composition of claim 13, wherein said smokeformulation further comprises a boron-containing compound.
 18. Thecomposition of claim 1, further comprising a combustion component. 19.The composition of claim 18, wherein said combustion component comprisessucrose, lactose, glucose, fructose, sorbitol, threose, erythritol,pentaerythritol, or a combination thereof.
 20. The composition of claim19, wherein said combustion component further comprises an chlorateoxidizer.